1. Field of the Invention
The invention relates to luminaires, and more particularly, to luminaires of the type having a generally opaque reflector adapted to reduce undesired glare and stray light yet provided with supplemental light modifying means to very substantially improve both the visual utility and the efficiency of the luminaire, and to substantially reduce its first cost, maintenance cost, and energy consumption. The invention applies to space lighting generally, and in particular to both indoor and outdoor lighting, and especially to roadway lighting.
2. Description of the Prior Art
Known roadway lighting commonly includes a luminaire having a light source disposed with a reflector equipped with transparent glassware or a plastic enclosure or a skirt, adapted to control light distribution. In addition, the enclosure is adapted to protect the light source from the natural elements or from vandalism. These enclosures collect dirt, and tend to absorb and redirect some of the light they transmit, in unwanted directions. An appreciable percentage of the light that would otherwise usefully illuminate a roadway is diffused and deflected into unwanted and objectionable directions. For example, some stray light is lost skyward, and some is often redirected toward bedroom windows of nearby residences or at high angles approaching the horizontal causing objectionable glare for drivers of approaching automobiles. These enclosure are very expensive, their production is energy-intensive, and they are generally made unnecessarily heavy in order to reduce breakage by vandalism.
If the roadway luminaire is designed so that the reflector extends down further around the enclosed light source and if the enclosing glassware or plastic were to be entirely omitted, the objectionable glare from a well-designed street luminaire would be almost entirely eliminated. However, such a design would render the light practically invisible at a substantial distance. This disadvantage eliminates the important "beacon effect" that alerts automobile drivers to distant curves in the roadway as they drive at night.
Accordingly, it is an important object of the invention to provide a roadway luminaire having a reflector without glassware or a plastic enclosure. The luminaire substantially minimizes glare by carrying the reflector down around the light source so that no appreciable light is lost beyond the margins of the roadway, nor at vertical angles close to the horizontal, nor upward. It is the teaching of this invention to preserve the beacon effect in such a luminaire by a light aperture in the side or sides of the reflector opposite the enclosed light source, whereby the light source may be seen at a distance without glare or any substantial loss of light.
It is a further object of the invention to assemble a transflector (beam splitter) in such a light aperture in order that some of the light directed toward the aperture will be reflected back usefully, while the remainder will be transmitted toward the roadway.
Known interior lighting is likewise provided commonly with transparent diffusing enclosures, usually flat, or else with glare-shielding louvers, which conceal the lamp itself from view at angles approaching the horizontal, and which augment the downward component of light, but at the cost of a substantial reduction in luminous efficiency.
It is still a further object of the invention to substitute a transflector, or "beam splitter" in place of such louvers or enclosures, in order to suppress all glare without the substantial light losses common to prevailing practice, while at the same time reducing the original and maintenance costs of such lighting.